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iDEA: Drexel E-repository and Archives > Drexel Academic Community > College of Engineering > Department of Materials Science and Engineering > Faculty Research and Publications (MSE) > Non-heavy-metal ZnS quantum dots with bright blue photoluminescence by a one-step aqueous synthesis

Please use this identifier to cite or link to this item: http://hdl.handle.net/1860/1665

Title: Non-heavy-metal ZnS quantum dots with bright blue photoluminescence by a one-step aqueous synthesis
Authors: Li, Hui
Shih, Wan Y.
Shih, Wei-Heng
Issue Date: Apr-2007
Publisher: Institute of Physics
Citation: Nanotechnology, 18(20): pp. 205604-1 - 205604-6.
Abstract: We have examined the aqueous synthesis of non-heavy-metal ZnS quantum dots (QDs) using 3-mercaptopropionic acid (MPA) as the capping molecule at various pH and MPA:Zn:S ratios. Transmission electron microscopy (TEM) and x-ray diffraction (XRD) indicated that the aqueous ZnS QDs were 3–5 nm in size with a zinc blende structure. We showed that, at pH 12 with a MPA:Zn:S = 8:4:1 ratio, the ZnS QDs with optimal blue emission could be obtained in a one-step, room-temperature aqueous process that exhibited a quantum yield of 31%, higher than that of the commercial CdSe/ZnS core–shell QDs. The present ZnS QDs could pass through a 50 kD filter. This indicated that they were smaller than 5 nm in size, consistent with those estimated from the UV–vis absorption edge and the TEM image. At a lower pH (e.g. pH = 8), the room-temperature synthesized ZnS QDs exhibited no photoluminescence. Although further hydrothermal annealing at 100 ◦C could improve the photoluminescence of the ZnS QDs, the resultant emission was not as bright as that obtained at pH 12 at room temperature. The blue emission of aqueous ZnS QDs was likely the result of trap-state emissions involving the defect states of the QDs. The present ZnS QDs were bright, small and contained non-heavy-metal elements, thus offering the potential for in vivo bioimaging.
URI: http://dx.doi.org/10.1088/0957-4484/18/20/205604
http://hdl.handle.net/1860/1665
Appears in Collections:Faculty Research and Publications (MSE)

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